Workplace wellness is a rapidly growing, $6 billion industry in the United States. Nearly all firms with 200 or more employees that offer health benefits also offer a wellness program. To encourage take-up, the Affordable Care Act allows employers to financially reward participation in workplace wellness programs by up to 50 percent of the cost of health insurance coverage. Yet, there is little rigorous evidence available on the effectiveness of workplace wellness, partly because the voluntary nature of these programs means that participants may differ from nonparticipants for reasons unrelated to the causal effects of the wellness program. In this project we seek to overcome this barrier by implementing a randomized control trial of workplace wellness. We will also provide the first analysis of the distributional effects of these programs. This will allow us to determine whether or not they effectively shift costs onto the unhealthy, which can occur if these programs differentially attract healthy employees. We will implement our randomized experiment on a large university campus. It will consist of an initial survey and health-risk assessment, followed by a set of optional wellness activities such as weight-management and recreation classes. A second survey and health- risk assessment will take place one year later. We will experimentally vary the financial incentives and wellness program subsidies offered to participants. We will also assign some employees to a control group that neither receives a health-risk assessment nor participates in wellness activities. In Aim 1 we will compare participation among individuals who receive large incentives to individuals who receive small incentives to document how those incentives affect the level of participation. In Aim 2 we will compare preexisting health measures among those same individuals to estimate how incentives affect the composition of participation. In Aim 3 we will compare outcomes among the participants to outcomes among the control group to estimate the causal effect of workplace wellness on employee health and well-being. Finally, in Aim 4 we will compare the effectiveness of financial incentives with that of wellness program subsidies. The primary contribution of our project is the use of a randomized controlled trial to establish causal estimates of the effect of workplace wellness programs on health, medical utilization, and well-being, and to provide the first measure of the distributional effectsof these programs.